People pushing to the front is the worst for me. It's fine if there is space but when I have been standing for a while and got up as far as I could peacefully and then some train of 10 people shove their way past me and then decide where I used to be standing is now where they are going to stand, it really pisses me off. I will usually either tap some shoulders and say KEEP MOVING or just move myself back in front of them even if I am standing on their toes. They usually get the idea.